Abstract: A tension controller for controlling the tension of running paper web. When a rotary press starts to operate and performs a minimum speed operation, the controller balances the tension of the paper web between a floating roller and a dancer roller, thereby easily bringing the dancer roller to the central position of its swing stroke. Also, the tension controller deactivates a dancer roller positioning mechanism in accordance with an acceleration signal before an impression on signal for starting printing is issued, thereby smoothly initiating tension control from the beginning of printing. Further, the displacement range of the dancer roller is divided into a plurality of regions. Based on values detected by three detection sensors for the dancer roller, namely a displacement direction detection sensor, a displacement speed detection sensor, and a displacement position detection sensor, the tension controller controls the driving time of an infeed roller drive transmission regulation unit.